The present invention relates to a cleaning device and a developing device incorporated in a facsimile apparatus, printer or similar electrophotographic apparatus. More particularly, the present invention is concerned with a cleaner and toner magazine (abbreviated as CTM hereinafter) having a cleaning unit and a developing unit constructed integrally with each other. The cleaning unit has a cleaning blade for removing a toner left on a photoconductive element after image transfer, and a waste toner tank for collecting it, while the developing unit has a fresh toner tank storing a fresh toner.
It is a common practice with an electrophotographic apparatus to form a latent image electrostatically on an image carrier, e.g., photoconductive element, develops the latent image with a developer, i.e., toner to produce a corresponding toner image, and then transfer the toner image to a paper. The paper has the toner image fixed by heat and then driven out of the apparatus as a recording. The toner left on the photoconductive element after the image transfer is scraped off by a cleaning blade and then collected in a waste toner tank. A discharge lamp illuminates the cleaned surface of the photoconductive element to dissipate charges also left on the element. The current trend in the electrophotographic apparatuses art is toward user-oriented maintenance including replenishment of a fresh toner and the collection of a waste toner. For this purpose, the manipulation for maintenance should be simplified. However, a fresh toner tank and the waste toner tank have customarily been constructed separately from each other, forcing the user to replace them one by one by a troublesome procedure. Further, in the conventional apparatus, the waste toner tank has to be provided with a sensor responsive to a condition wherein the tank has been filled up with the waste toner.
To eliminate the above problems, there has been proposed a system in which the photoconductive element, developing device, fresh toner tank, cleaning device and waste toner tank are constructed into a unit: when, for example, the fresh toner tank runs out of toner, the unit is bodily replaced. This, however, increases the cost of the unit as well as the running cost per paper since, for example, the photoconductive element, developing device, cleaning device and waste toner tank which are still usable have to be discarded together with the empty fresh toner tank. Moreover, toxic substances are contained in the unit and apt to invite environmental pollution when the unit is discarded. Although the manufacturer may collect and refill the fresh toner tank, even the photoconductive element, developing device, cleaning device and waste toner tank not directly contributing to toner replenishment have to be transported, resulting in an extra transport cost.
In the light of the above, there has also been proposed a CTM in which the fresh toner tank and waste toner tank are constructed integrally with each other. The CTM, which is bodily replaceable, simplifies maintenance, eliminates the need for the sensor responsive to the full state of the waste toner tank, and solves the environmental pollution problem. In the conventional CTM, the fresh toner tank is fully independent of the developing device and replenishes it with a toner via a long transport path implemented by a motor, screw, guide, agitator, etc.
With an electrophotographic apparatus using such a CTM, the user is expected to perform maintenance including the replenishment of a fresh toner and the collection of a waste toner. It is, therefore, preferable that the manipulation for maintenance be simple, and the frequency of replacement of the CTM be low. To reduce the frequency of replacement, each of the fresh toner tank and waste toner tank should advantageously be provided with a great capacity. However, such bulky tanks are disadvantageous from a space saving standpoint. Further, the fresh toner tank run out of toner simply wastes the space and, in addition, degrades cost performance of the apparatus since it is made up of a number of members for effecting efficient replenishment. Moreover, since the toner is transported over a long transport path, the quality thereof and, therefore, image quality is apt to fall.
On the other hand, an electrophotographic apparatus of the type described is practicable with one of two different charging methods, i.e., a corona charging method and a contact charging method. The corona charging method, which uses a corona charger, is predominant today since it is capable of charging the photoconductive element uniformly over a long period of time. By contrast, the contact charging method holds a charger in contact with the photoconductive element. This kind of method is susceptible to the contact condition of the charger with the photoconductive element and the surface condition of the element. With the contact charging method, therefore, it is difficult to charge the photoconductive element uniformly over a long period of time. For example, it is likely that toner particles, paper dust and other impurities deposited on the photoconductive element are transferred to the charger, e.g., charge roller, lowering the charging ability of the charger due to contamination.
However, the contact charger is advantageous over the corona charger in that it produces a minimum of ozone during operation, and in that it is operable with a low voltage. The reduction of ozone, among others, meets the increasing demand for improved office environments. For this reason, the increase in the cost of equipment to be operated in offices is generally accepted. In this situation, the prerequisite is that the contact charger be replaced periodically, and that the deterioration of such a charger due to aging be slowed down.